Science update: How much red meat is safe?

We’re a red-meat eating nation, but just how much is too much? Paula Goodyer investigates.

It feels like we’re caught in a tug of war over red meat. On one side are the meat-loving people from planet paleo, while on the other are headlines claiming red meat causes cancer. We investigate both sides of the story.

The good news

Key iron source

Besides being a great source of protein, zinc and B vitamins, red meat is also an easily-absorbed source of iron, which helps prevent anaemia.

In New Zealand, around 15-18 per cent of women aged 15-50 years have iron deficiency, with 5-6 per cent of those having iron-deficiency anaemia. Symptoms of deficiency can include low energy and pale skin. So, eating more red meat is a good way to meet your daily iron requirements.

A protein fix

Meat is one of the best sources of protein. This is not only beneficial for building muscles, but it is also very important for keeping you feeling full, so you’re less likely to overeat between meals.

People who avoid meat often do so out of concern that the fat content will make them gain weight when, in fact, the protein in meat helps with satiety. And, by using lean meat, it’s easy to stay within the recommended limits for saturated fat.

The not-so-good news

The heat’s on processed meats

Research links diets high in red meat, especially processed meats such as bacon, salami and sausages, to an increased risk of disease.

The World Health Organization (WHO) has declared processed meats as Class 1 carcinogens. This means there is strong evidence these meats cause cancer.

Risk of bowel cancer

The evidence against eating too much red meat is strongest for bowel cancer, New Zealand’s second largest cancer killer.

So, why does overconsumption increase our risk of bowel cancer?

The high amounts of iron may cause damage to our cells and encourage tumour growth.

Harmful chemicals are created when meat is cooked, especially burnt or charred.

Preservatives in processed meat, called nitrates and nitrites, could be the culprits.

It’s also possible a high red meat intake increases cancer risk because it leaves less room for protective foods like vegetables, legumes and fruit.

Three ways to keep meat on the menu

1. Be portion wise

Stick to small portions of lean red meat (eg. beef, lamb or pork). Ideally, a serving should be no more than the size of your palm, with a maximum of 700-750g raw weight (500g cooked) meat per week, according to the WHO. So, eating a 125-150g (raw weight) portion of red meat 3-4 times a week is easily within the guidelines. For a family of four, that’s around 500-600g of raw meat for a meal.

2. Go easy on processed meats

If ham, bacon and sausage are staples, think again. It’d be best to relegate them to a very occasional treat instead. The Ministry of Health’s Eating and Activity Guidelines for New Zealand Adults advise us to eat a wide variety of protein foods, which may include red meat with the fat removed. They also highlight that processed meats are often high in both fat and salt and are linked to a higher risk of colorectal cancer.

The World Cancer Research Fund takes a much stronger stand, recommending we avoid processed meat altogether.

3. Cook it slow and low

Cooking your meat at very high temperatures, or in direct contact with a flame or hot surface, such as on a searing hot barbecue or frying pan, produces harmful chemicals. These include polycyclic aromatic hydrocarbons (PHAs) and heterocyclic aromatic amines (HCAs).

Although studies show these chemicals can cause cancer in animals, it’s hard to determine what the effect of cooked meats is on humans. But some studies have found that high intakes of well-done, barbecued or fried meat are associated with an increased risk of developing bowel, prostate and pancreatic cancers.

Cooking meat over very high heat also produces other harmful chemicals called Advanced Glycation End Products (AGEs). These have been linked to diseases such as type 2 diabetes and Alzheimer’s.

So, avoid burning your meat, and cook it slowly. Poaching and steaming are the healthiest methods. If you are cooking on a barbecue, using a marinade with acidic ingredients like lemon juice or vinegar with your meat, poultry and fish, will reduce the level of HCAs, PHAs and AGEs.

Link with diabetes

A large US study found that people who ate less red meat and more dietary fibre had a reduced risk of developing type 2 diabetes.

“It’s an association. We can’t say that eating less meat is the sole reason for a reduced risk of type 2 diabetes,” dietitian and Reversing Diabetes author Alan Barclay says.

“The nitrate preservatives used in processed meat have been linked to insulin resistance, which increases the risk of type 2 diabetes,” Dr Barclay says.

“Processed meats like bacon and sausages are often fried at high temperatures, which can produce harmful substances like heterocyclic amines, so that might also play a role.

“The best advice is to have processed meat no more than once a week,” Dr Barclay says.

A heart stopper

Then there’s heart disease. “The fat found in and around meat, and especially processed meat, is linked to a higher risk of heart disease, but it’s an association, which isn’t the same as saying it’s a cause,” Baker IDI Heart & Diabetes Institute cardiologist Paul Nestel says. “It may be the salt and nitrates that are the problem,” Professor Nestel says.

By contrast, unprocessed meat such as a lean steak is less problematic.

“Most researchers agree that having lean meat in moderation – say three times a week – is safe,” he says.

The Cancer Society recommends eating red meat on no more than three or four days a week.

The paleo picture

Paleo fans believe that a diet based on what our ancient ancestors ate is good for our health.

But, the meat that hunter-gatherers ate wasn’t from domestic animals that spend their days lazily grazing in lush, green pastures.

Instead, they ate the meat of animals that ran around in the wild and had a different fat profile, with less saturated fat and more healthy omega-3 fats.

The final say…

So, if too much red meat can set us up for health problems, should we all go vegetarian?

Compared with meat eaters, vegetarians tend to eat less saturated fat and more fibre, potassium, magnesium and plant nutrients, according to Harvard Medical School. As a result, they often have healthier levels of cholesterol and blood pressure, and a lower body mass index, all of which are linked to a reduced risk of chronic disease.

Studies of groups of Seventh-Day Adventists, who are largely vegetarian, also show a slightly lower risk of bowel cancer, but the evidence isn’t strong enough to recommend that everyone should eat a vegetarian diet.

The bottom line is, you can get many of the health benefits of a vegetarian diet without avoiding meat entirely. Instead of making meat the focus, prepare meals with an emphasis on plant-based foods and only include small amounts of unprocessed meat.